Various types of flowmeters have been developed over the years for measuring the flow of fluid mediums such as liquids gases, liquid/gas mixtures, slurries, etc. Most flowmeters, such as pelton type or paddle wheel flowmeters are subject to certain inaccuracies depending upon temperature, fluid consistency, turbulence of the flowing fluid and various other factors. Nevertheless, pelton type flowmeters can be appropriately calibrated with respect to the fluid to be measured that measurement of flow can be quite accurate. Positive displacement flowmeters of various types are considered to be quite accurate in comparison with pelton type flowmeters but their accuracy can be subject to deterioration by such factors as pressure loss across the flowmeter rotors, magnetic field induced rotor retardation, etc. It is desirable, therefor, to provide a positive displacement type interengaging rotor flowmeter construction which has very little pressure loss across the rotors and which is not subject to any magnetic retardation.
Another factor that contributes to inaccuracy of dual rotor type positive displacement flowmeters is the presence of hydraulic shock at the rotor interface which contributes to pressure loss and which results in flowmeter inaccuracy. It is desirable, therefor, to provide a positive displacement type flowmeter wherein hydraulic shock across the flowmeter rotors is significantly minimized.